In 1833, a young priest of the diocese of Le Mans, Dom Prosper Guéranger, undertook the restoration of benedictine monastic life on the site of an old priory at Solesmes, after forty years of silence due to the French Revolution. He seized upon the restoration of Gregorian chant with enthusiasm and began by working on its execution, asking his monks to respect the primacy of the text in their singing: pronunciation, accentuation and phrasing, with an eye to guaranteeing its intelligibility, in the service of prayer. Dom Guéranger also placed the task of restoring the authentic melodies into the hands of one of his monks.

The handwriting, in “thin flyspecks”, of the original manuscripts was indecipherable at the time. But the invention of photography soon brought unforeseen benefits with it. Little by little, an incomparable collection grew at Solesmes, facsimiles of the principal manuscripts of the chant contained in the libraries of all Europe. This was the genesis of the Paleography of Solesmes.

There is 13 more manuscripts available In the virtual Library Codices Electronici Sangallenses (CESG), among them important codices with neumatic notation including Cantatorium — the earliest complete extant musical manuscript in the world (922 — 925):

Great new source of information about chant manuscripts and also source of chant scores is available online on the site Gregofacsimil. Website is in French language. If you don’t understand French at all, you can try automated translations: English, German. On the page you can find introduction to problematic of restitution of chant melodies, some of its results — especially responsories of selected matins (night part of officium) and also whole matins for some feasts (I haven’t seen scores of matins anywhere else on the net).

Abbey Library of St. Gallen (Switzerland) is available online! Or at least part of it. At the moment, you can study 144 medieval manuscripts on the Website Codices Electronici Sangallenses (CESG), among them important codices with neumatic notation including famous Codex Hartker: